+1 for Malossi & Polini parts
Go for it!
The weights and contra spring require lots of testing, it's all about trial and error. Remember that when you change something around the engine, giving it more power (better pipe, bigger jets, performance air filter, big bore kit etc.) then the way the CVT responds will change too. So the CVT upgrades should be done at the end, and their purpose is to give you the possibly best performance out of the power that you already have.
Once you buy all the stuff for the upgrades (variator, clutch, etc.) and install it, give the bike a good test run. For starters go with the rollers that will come together with the variator kit. Then if the engine will overrev, it will mean that your contra spring is too stiff / the rollers are too light. If the bike will be sluggish, it will mean that the rollers are too heavy. I would go for a soft contra spring (especially since you don't ride on hills).
I would say that you might want to leave the stock contra spring, like I did. It's very nice stuff. If your OEM parts are shot, I would buy the Malossi variator, clutch and torque controller and go with the stock spring. Then test it and the way your bike will behave will tell you if you need to change the roller's weight, and if so, whether to go up or down on the weight.
